The present invention relates to a single cylinder deadbolt lock with thumbturn and particularly to such a lock wherein the thumbturn is selectively disengaged according to the manner in which the lock is operated.
Single cylinder deadbolt locks are generally restricted in their application to residences because of security disadvantages. For example, a single cylinder lock with a thumbturn on the inside of the door is easily operated by an intruder to gain exit from the premises for easy removal of stolen merchandise after break-in through some other means such as a window or the like. The only security hardware locking device available for effectively solving this problem has been the double cylinder deadbolt lock. However, this type of lock is not recommended for residential uses simply because of the difficulty entailed in exiting from the locked premises. The double cylinder lock requires the use of a key on the inside of the door to effect exit and therefore its use is not considered advisable because of possible difficulty in locating a key and inserting the key in the lock in an emergency. Thus a conflict exists between usual police and fire department concepts relating to security and easy exit features.